A pile of $n$ rings, each ring smaller than the one below it, is on a peg. Two other pegs are attached to a board with this peg. In the game called the Tower of Hanoi puzzle, all the rings must be moved to a different peg, with only one ring moved at a time, and with no ring ever placed on top of a smaller ring. Find the least number of moves (in terms of $n$ ) that would be required.